1. Field of the Invention
The present invention relates to a printed wiring board having a core substrate and upper and lower buildup layers.
2. Description of Background Art
Japanese Laid-Open Patent Publication No. 2011-100908 relates to a printed wiring board having through holes (penetrating holes) formed using a laser. The printed wiring board of Japanese Laid-Open Patent Publication No. 2011-100908 has through holes that become narrower from an upper surface of the core substrate toward a lower surface and through holes that become narrower from the lower surface toward the upper surface so that warping of the printed wiring board is reduced. Semiconductor devices may be manufactured by mounting IC chips on printed wiring boards. Such mounting may be conducted through a reflow process. The entire contents of this publication are incorporated herein by reference.